The present invention relates a crossmember for a vehicle frame and, more particularly, the present invention relates to a tubular crossmember for use with a pair of spaced apart C-shaped rails in the construction of a truck or tractor frame.
Weight is one of the most important factors in the design of an over the highway truck or tractor. Fleet owners are often paid by the ton/mile. Highway regulations set maximum weights for loaded trucks and tractors. As a result, the lighter the over the highway truck or tractor is, the more profitable it is. Even a small decrease in the weight of an over the highway truck or tractor greatly increases the profitability of the truck or tractor over its life.
In over the highway trucks and tractors, it is common to use a frame that includes a pair of parallel frame rails of a C-shaped cross-section that are spaced apart by crossmembers. The C-shaped rails run longitudinally along the length of the truck. The crossmembers are attached to the side rails to form a ladder type frame. Prior art crossmembers are thick, heavy members, because they are designed to carry loads applied to the crossmember from several different directions. The additional weight of prior art crossmembers reduces the profitability of the truck.
Two types of loads applied to truck and tractor frames are the result of frame roll and parallelogramming. Frame roll is the result of an offset load applied to the frame by a bracket that supports a heavy article, such as a fuel tank, a battery box, or a suspension support. The offset load creates a torsional stress or roll in the frame. The torsional stress or roll in the frame increases as the truck or tractor is driven around a bend and along uneven roads.
Parallelogramming occurs when the truck or tractor is steered to corner tightly or when one tire of the truck or tractor hits a pothole. These conditions cause the rails of the truck frame to move longitudinally with respect to one another.
Prior art crossmembers are designed to prevent both frame roll and parallelogramming. Because prior art crossmembers are designed to carry loads applied from more than one direction the crossmembers are required to be heavy. The heavy prior art crossmembers account for a significant portion of weight to the over the highway truck or tractor.
What is needed is a crossmember that is designed to carry a load in one direction while remaining flexible in other load conditions. A crossmember that carries a load in one direction but remains flexible in other load conditions is lighter and less expensive than crossmembers designed to carry loads from multiple directions. Use of lighter crossmembers in vehicle increases the load that can be carried. As a result, the profitability of the vehicle is increased.
The present invention concerns a crossmember for a vehicle frame having spaced apart rails. The crossmember includes a first substantially S-shaped member that has first and second bent end portions. A second substantially S-shaped member also includes first and second bent end portions. The first and second S-shaped members are connected at an intersection of the first and second S-shaped members near longitudinal centers of the elements. A first substantially C-shaped member includes first and second bent end portions. The first bent end portion of the first C-shaped member is connected to the first bent end portion of the first S-shaped member. The second bent end portion of the first C-shaped member is connected to the second end portion of the second S-shaped member. A second substantially C-shaped member also includes a first bent end portion and second bent end portion. The first bent end portion of the second C-shaped member is connected to the first bent end portion of the second S-shaped member. The second bent end portion of the second C-shaped member is connected to the second bent end portion of the first S-shaped member.
In embodiments of the invention the first and second S-shaped members are pivotally connected. The S-shaped members and the C-shaped members are hollow tubes that are compressed at their ends. The ends of the S-shaped members and the C-shaped members are constrained between pairs of solid plates.
A vehicle frame of the present invention includes a spaced pair of rails separated by one or more tubular X-shaped crossmembers. The X-shaped crossmembers include a pair of tubular elements pivotally connected at locations near respective longitudinal centers of the elements. Each of the elements have spaced curved end portions. End anchors secure the end portions to the rails such that the X-shaped crossmembers secure the rails in a spaced relationship.
The crossmember connection that is used to connect the tubular crossmember to rails of the vehicle frame includes an outer plate and an inner plate. The outer plate includes a flat portion that mates with the frame rail and a curved portion that conforms to the tubular crossmember. The inner plate includes a flat and curved portions that conform to the tubular crossmember. The end portions of the tubular members of the crossmember is held between the inner plate and the outer plate which absorb forces and moments that would otherwise be absorbed by the tubular members. The curved portions of the inner and outer plates extend away from the tubular members.
In an embodiment of the invention, the curved portion of the inner plate has a radius of curvature that is less than a radius of curvature of a bend of the tubular member. The curved portion of the outer plate includes a first bend generally conformed to a bend of the tubular member and a second bend that curves away from the tubular member. The inner and outer plates include mounting holes that are in alignment with mounting holes in the bent end portions of the tubular members of the crossmember.
The tubular crossmember of the present invention is designed to withstand a load in one direction while remaining flexible in other load directions. The single direction load absorbing design of the present invention minimizes crossmember weight, expense and optimizes material placement. Reduction in the weight of the frame results in increased revenue produced by the truck over the life of the truck. The use of several of the crossmembers of the present invention produces an efficient crossed truss structure between the rails. The truss structure is efficient in carrying only tensile compressive forces in the tubular member.
The crossmember connection of the present invention transfers loads from the truss to the bolts with plates that are added only to the ends of the crossmember to carry bending and shear forces. The small plates carry the bending moments of the crossmembers and add little weight to the crossmember.
The disclosed crossmember design efficiently carries moment and shear forces in the plane of the tube sections. The disclosed crossmember is flexible in other load directions such that it easily conforms and does not increase stresses in the mounting brackets. The shape of the single direction crossmember allows a horizontal crossmember to be placed above and below a vertical crossmember with all of the bolts at the same height on the rail. The crossmember of the present invention is less expensive than traditional crossmembers and is much lighter. It is optimized to carry load in one direction. The center tubes carry only tension and compression in a truss system. The tubes of the crossmember are efficient to prevent buckling. The tubular members are easily compressed at their ends to accommodate mounting. High bending stress is carried by the thick connection plates. The crossmember is very flexible in frame torsion and out of plain loads and has a very small footprint on the frame.
These and other advantages of the present invention will become apparent upon reading the following detailed description in view of the drawings.